Metro area air quality · 2025

Mount Vernon, OH

Median AQI 39 (Good). 85.3% of monitored days rated Good across this metro's EPA monitoring network.

39
Median AQI
85.3%
Good-air days
1
Unhealthy days
79%
Cleaner than US metros

Mount Vernon, OH posted a 2025 median AQI of 39 (Good) with 85.3% Good days

According to the U.S. EPA Air Quality System, the Mount Vernon, OH CBSA recorded a median AQI of 39 across 245 monitored days in 2025, with 85.3% rated Good and 1 unhealthy or worse. This is an annual metro comparison, not a live advisory.

Data source EPA Air Quality System (AQS)

Cleaner than US metros
The Mount Vernon, OH CBSA's 85.3% Good-day share places it cleaner than 79% of US metros in 2025.
Closest median-AQI peer
Bay City, MI (70.4% Good, median AQI 39) is the closest nationwide median-AQI peer to Mount Vernon, OH.
2020–2025 Good-day shift
Mount Vernon, OH's Good-day share moved -6.6 points from 2020 to 2025 (median AQI +1).
Median AQI
Median AQI: 39

Aggregated from EPA Air Quality System (2025), 245 monitored days. EPA AQS →

The verdict

Mount Vernon, OH sits in the upper Good-day tercile among EPA CBSA metros on this site (85.3% of 245 monitored days). On the EPA scale the metro runs good, cleaner than most US metros, with a median AQI of 39 and 85.3% of 245 monitored days in the Good band.

39
median AQI · Good
85.3%
days rated Good
79%
cleaner than US metros
159
worst single reading

1 day reached Unhealthy or worse across the metro's monitors in 2025.

Annual release change

What changed in the 2025 EPA annual release

2024 → 2025
  • Mount Vernon, OH metro's peak single-day AQI rose from 101 to 159 between the 2024 and 2025 EPA annual releases, a change of +58 points.
  • Mount Vernon, OH metro's Unhealthy-category days rose from 0 to 1 between the 2024 and 2025 EPA annual releases, a change of +1 days.

Compared against 244 monitored days in 2024 and 244 in 2025. These are arithmetic differences between two stored EPA annual summaries, not a cause claim or a live advisory.

National release changes Two-year CSV

Mount Vernon, OH sits in the upper Good-day tercile among EPA CBSA metros on this site (85.3% of 245 monitored days). Signature read: 85.3% Good-day share (high tercile vs CBSA corpus). Aggregated EPA AQS monitors across this Core-Based Statistical Area logged a median Air Quality Index of 39 over 245 measured days in 2025 (Good / Good). The monitored-day split lands at 209 Good (85%), 34 Moderate (14%), and 1 Unhealthy-for-Sensitive-Groups (0%). The 90th-percentile AQI finished at 54; the highest single-day reading hit 159 (Unhealthy).

Across 2020–2025, Good-day share shifted -6.6 points and median AQI moved +1 (worsening). The annual record contains 1 day at Unhealthy or worse. Metros with comparable AQI profiles include Bay City, MI (70.4% good, AQI 39); Brainerd, MN (74.3% good, AQI 39); Cambridge, MD (86.0% good, AQI 39).

Health effects of air pollution →

Air Quality Summary

Median AQI

39

Good

Good Days

85.3%

209 of 245 days

Max AQI

159

Unhealthy

Health Grade

Good

90th pct: 54

AQI Day Breakdown (2025)

Distribution of 245 monitored days across EPA AQI categories.

Good

209

85%

Moderate

34

14%

USG

1

0%

Unhealthy

1

0%

Very Unhealthy

0

0%

Hazardous

0

0%

Health Impact Assessment

Good

The Mount Vernon, OH metro area's air quality is rated Good based on 85.3% good air days. There were 1 unhealthy days in 2025 when outdoor activity should be limited.

Air quality is acceptable most days, but 1 days reached "Unhealthy for Sensitive Groups" and peak AQI reached 159. Sensitive groups should monitor real-time conditions at AirNow.gov.

How does the Mount Vernon, OH metro compare?

How Mount Vernon, OH compares

Good-day share better than typical
Mount Vernon, OH 85.3%
Bay City, MI 70.4%
Typical US metro 70.6%
Median AQI better than typical
Mount Vernon, OH 39
Bay City, MI 39
Typical US metro 41
Unhealthy days / yr about typical
Mount Vernon, OH 1
Bay City, MI 0
Typical US metro 1

5-Year Air Quality Trend

Air quality is worsening in the Mount Vernon, OH metro. Highest Good-day share: 2020 (92.2%, 226 of 245 monitored days).

Year Good Moderate Unhealthy Median AQI
2020 226 19 0 38
2021 225 20 0 38
2022 225 19 0 39
2023 200 44 0 42
2024 208 36 0 41
2025 209 34 1 39

Metros with a similar median AQI

CBSA peers nationwide whose annual median AQI sits near Mount Vernon, OH (39).

Bay City, MI

Median AQI 39 · 70.4% Good-day share

39

Brainerd, MN

Median AQI 39 · 74.3% Good-day share

39

Cambridge, MD

Median AQI 39 · 86.0% Good-day share

39

Charleston, WV

Median AQI 39 · 77.0% Good-day share

39

Dalton, GA

Median AQI 39 · 90.3% Good-day share

39

Harrisonburg, VA

Median AQI 39 · 80.0% Good-day share

39

Metros with similar unhealthy-day exposure

A second relationship type: metros whose unhealthy-or-worse day count is closest to Mount Vernon, OH's 1 (independent of median AQI).

Ann Arbor, MI

1 unhealthy-or-worse days · median AQI 41

41

Bangor, ME

1 unhealthy-or-worse days · median AQI 33

33

Baraboo, WI

1 unhealthy-or-worse days · median AQI 35

35

Bartlesville, OK

1 unhealthy-or-worse days · median AQI 44

44

Beaumont-Port Arthur, TX

1 unhealthy-or-worse days · median AQI 52

52

Beaver Dam, WI

1 unhealthy-or-worse days · median AQI 40

40

Frequently Asked Questions

How many unhealthy air days does Mount Vernon, OH have? ▼
In 2025, the Mount Vernon, OH metro area recorded 1 unhealthy air days (1 Unhealthy, 0 Very Unhealthy, 0 Hazardous). The maximum AQI reached 159.
What is the air quality in the Mount Vernon, OH metro area? ▼
The Mount Vernon, OH metro area has a median Air Quality Index (AQI) of 39, rated "Good." 85.3% of monitored days (209 out of 245) had good air quality in 2025.
Is air quality in Mount Vernon, OH getting better or worse? ▼
Air quality in the Mount Vernon, OH metro is worsening across floor-qualifying years (2020-2025); years with fewer than 100 monitored days are excluded from that direction. Highest qualifying Good-day share: 2020 at 92.2% (226 of 245 days). Lowest qualifying Good-day share: 2023 at 82.0% (200 of 244 days).
What does AQI 39 mean for health? ▼
An AQI of 39 is "Good", air quality is satisfactory and poses little or no health risk. This is the best category on the EPA's AQI scale.
How does Mount Vernon, OH compare to other metro areas? ▼
The Mount Vernon, OH metro has 85.3% good air days. Similar metros: Bay City, MI (70.4% good), Brainerd, MN (74.3% good), Cambridge, MD (86.0% good).
What is the 90th percentile AQI for Mount Vernon, OH? ▼
The 90th percentile AQI for the Mount Vernon, OH metro area is 54, meaning 90% of monitored days had an AQI at or below this level. The maximum AQI recorded was 159 (Unhealthy).

Data Sources

Primary Source: U.S. Environmental Protection Agency (EPA), Air Quality System (AQS), Annual AQI by CBSA dataset for Mount Vernon, OH, 2025. See our methodology for how AQI, median, and coverage figures are computed.

Read our methodology , how this data is sourced, computed, and verified.

Source: U.S. EPA Air Quality System (AQS) Annual AQI by CBSA summary, Mount Vernon, OH · 2020–2025